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Autism’s brain activity captured in diagnostic test

By Andy Coghlan

Characteristic patterns of electrical brain activity seen in children with autism could provide a new test for diagnosing the condition.

At present, autism is diagnosed by carefully observing a child’s behaviour and assessing their clinical history. Now, Frank Duffy of Boston Children’s Hospital and colleague Heidelise Als have developed an electroencephalogram (EEG) test that involves placing 24 electrodes on a child’s scalp.

This enabled them to identify 33 patterns of connectivity between brain regions that were strikingly and consistently different in 430 children with autism aged between 2 and 12, compared with 554 neurotypical controls.

“I’m very optimistic this data will provide a potential for early diagnosis,” Duffy says.

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The researchers analysed patterns of connectivity for all possible pairings of the 24 electrodes, amounting to more than 4000 in total. Duffy calls the patterns “coherence factors” because they are a measure of how well signals from different brain regions match up with each other. This reflects the strength of the connectivity between the regions from which the signals originated.

A key feature of autism is thought to be poor connectivity between brain regions linked with language. And as expected, the greatest differences between neurotypical and autistic children were in a pattern, called factor 15, which showed very poor connectivity in a part of the brain vital for language processing called the arcuate fasciculus.

Duffy says that the patterns seen were so consistent in so many of the children with typical autism that they could represent the first neuro-physiological “phenotype” of the disorder. “What stunned me was that a pattern of coherence differences could have this power,” he says. “It really does reflect the common physiological phenotype of autism.”

Duffy warns, however, that doctors shouldn’t rely on the test until it has been validated by other teams and compared against neurological conditions with which autism could be confused, such as Asperger’s syndrome.

If the test is validated, it could provide a much simpler and more reliable way of diagnosing the condition than any currently available, says Duffy. He points out that tests based on genetics are still a distant hope, and there are logistical problems with using fMRI to scan children’s brains, not least because they have to be sedated or anaesthetised to undergo the scans.

With the EEG, by contrast, the electrodes can be put in place within a few minutes because they come prefabricated into a head net. Patients can move around while wearing the net, and the readings only take 20 minutes at most.

“The idea of using EEG to diagnose autism is important,” says Simon Baron-Cohen, director of the Autism Research Centre in Cambridge, UK. “We need more research using this and related techniques, towards making diagnosis more objective and reliable, and hopefully they’ll also be quicker and cheaper,” he says.